Insights on the dissolution of water in an albite melt at high pressures and temperatures from a direct structural analysis.

The water dissolution mechanism in silicate melts under high pressures is not well understood. Here we present the first direct structure investigation of a water-saturated albite melt to monitor the interactions between water and the network structure of silicate melt at the molecular level. In situ high-energy X-ray diffraction was carried out on the NaAlSi3O8-H2O system at 800 °C and 300 MPa, at the Advanced Photon Source synchrotron facility. The analysis of the X-ray diffraction data was augmented with classical Molecular Dynamics simulations of a hydrous albite melt, incorporating accurate water-based interactions. The results show that metal-oxygen bond breaking at the bridging sites occurs overwhelmingly at the Si site upon reaction with H2O, with subsequent Si-OH bond formation and negligible Al-OH formation. Furthermore, we see no evidence for the dissociation of the Al3+ ion from the network structure upon breaking of the Si-O bond in the hydrous albite melt. The results also indicate that the Na+ ion is an active participant in the modifications of the silicate network structure of the albite melt upon water dissolution at high P-T conditions. We do not find evidence for the Na+ ion dissociating from the network structure upon depolymerization and subsequent formation of NaOH complexes. Instead, our results show that the Na+ ion persists as a structure modifier with a shift away from Na-BO bonding to an increase in the extent of Na-NBO bonding, in parallel with pronounced depolymerization of the network. Our MD simulations show that the Si-O and Al-O bond lengths are expanded by about 6% in the hydrous albite melt compared to those of the dry melt at high P-T conditions. The changes in the network silicate structure of a hydrous albite melt at high pressure and temperature, as revealed in this study, must be considered in the advancement of water dissolution models of hydrous granitic (or alkali aluminosilicate) melts.

Calculating the Enthalpy of Vaporization of Ethanol, n-Heptane, Isooctane, and a Binary Mixture of Isooctane + n-Heptane from Their Vapor Pressure Data.

ConspectusA key physical property of volatile liquids is vapor pressure (VP). Volatile organic compounds (VOCs) are a classification of compounds directly associated with low boiling points, high rates of evaporation, and high flammability. The majority of chemists and chemical engineers were directly exposed to the odor of simple ethers, acetone, and toluene in the air while taking an organic chemistry laboratory course as an undergraduate student. These are just a few examples of the numerous VOCs produced by the chemical industry. When toluene is poured into a beaker from its reagent bottle, its vapors readily evaporate at ambient temperature from this open container. When the cap is securely placed back on the reagent bottle of toluene, a dynamic equilibrium develops and exists in this closed environment. This chemical concept is known as a vapor-liquid phase equilibrium. A crucial physical property of spark-ignition (SI) fuels is high volatility. In the United States, most of the vehicles traveling on the road today have SI engines. Gasoline is the fuel used to power these engines. It is a major product manufactured by the petroleum industry. This fuel is petroleum based since it is a refined product of crude oil consisting of a mixture of hydrocarbons, additives, and blending agents. Thus, gasoline is homogeneous solution of VOCs.The VP as a function of temperature of a pure VOC can readily be measured using an ebulliometer. The VP is also known in the literature as the "bubble point pressure". In this investigation, the VP as a function of temperature was acquired for the VOCs ethanol, isooctane (2,2,4-trimethylpentane), and n-heptane. The latter two VOCs are primary reference fuels components found in 87, 89, and 92 grade gasoline. Ethanol is an oxygenate additive of gasoline. The VP of a homogeneous binary mixture of isooctane and n-heptane was also acquired using the same ebulliometer and methodology. In our work, an enhanced ebulliometer was used to collect the VP data in our work. It is known as the vapor pressure acquisition system. The devices that comprise the system automatically acquire the VP data and log it into an excel spreadsheet. The data are readily transformed into information to compute the heat of vaporization (ΔHvap). The results described in this Account compare quite favorably to the literature values. This validates our system for performing fast and reliable VP measurements.

Syntheses and structures of two benzoyl amides: 2-chloro-4-eth-oxy-3,5-dimeth-oxy-N-(3-oxo-cyclo-hex-1-en-1-yl)benzamide and 2-chloro-N-(5,5-dimethyl-3-oxo-cyclo-hex-1-en-1-yl)-4-eth-oxy-3,5-di-meth-oxy-benzamide.

The first title benzoyl amide, C17H20ClNO5 (3a), crystallizes in the monoclinic space group P21/c with Z = 4 and the second, C19H24ClNO5 (3b), also crystallizes in P21/c with Z = 8 (Z' = 2), thus there are two independent mol-ecules in the asymmetric unit. In 3a, the phenyl ring makes a dihedral angle of 50.8 (3)° with the amide moiety with the C=O group on the same side of the mol-ecule as the C-Cl group. One meth-oxy group is almost in the plane of the benzene ring, while the eth-oxy and other meth-oxy substituent are arranged on opposite sides of the ring with the eth-oxy group occupying the same side of the ring as the C=O group in the amide moiety. For one of the two mol-ecules in 3b, both the amide and 5,5-dimethyl-3-oxo-cyclo-hex-1-en-1-yl moieties are disordered over two sets of sites with occupancies of 0.551 (2)/0.449 (2) with the major difference between the two conformers being due to the conformation adopted by the cyclo-hex-2-en-1-one ring. The three mol-ecules in 3b (i.e., the undisordered mol-ecule and the two disorder components) differ in the arrangement of the subsituents on the phenyl ring and the conformation adopted by their 5,5-dimethyl-3-oxo-cyclo-hex-1-en-1-yl moieties. In the crystal of 3a, N-H⋯O hydrogen bonds link the mol-ecules into a zigzag chain propagating in the [001] direction. For 3b a combination of C-H⋯O and N-H⋯O inter-molecular inter-actions link the mol-ecules into a zigzag ribbon propagating in the [001] direction.

N-Butanoyl-N-(3-chloro-1,4-dioxonaph-thalen-2-yl)butanamide.

In the title compound, C18H18ClNO4, the imide group with its two alkyl substituents is approximately perpendicular to the plane of the naphtho-quinone ring system [dihedral angle = 78.5 (1)°]. Further, the imide carbonyl groups are oriented in an anti sense. In the crystal, the substituted naphtho-quinone rings form π-π stacks in the a-axis direction [perpendicular centroid-centroid distance = 3.209 (2) Šand slippage = 4.401 Å].

Synthesis and characterization of novel unsymmetrical and symmetrical 3-halo- or 3-methoxy-substituted 2-dibenzoylamino-1,4-naphthoquinone derivatives.

Symmetrical and unsymmetrical 3-halo- or 3-methoxy- substituted 2-dibenzoylamino- 1,4-naphthoquinone analogs were synthesized with an average yield of 45% via sodium hydride promoted bis-acylation of 2-amino-3-chloro-1,4-naphthoquinone, 2-amino-3-bromo-1,4-naphthoquinone and 2-amino-3-methoxy-1,4-naphthoquinone.

Monitoring synchrotron X-ray-induced radiolysis effects on metal (Fe, W) ions in high-temperature aqueous fluids.

Radiolysis-induced effects on aqueous tungsten ions are observed to form a precipitate within seconds upon exposure to a synchrotron X-ray micro-beam in a WO(3) + H(2)O system at 873 K and 200 MPa. In situ Fe K-edge energy-dispersive X-ray absorption spectroscopy (ED-XAS) measurements were made on Fe(II)Cl(2) aqueous solutions to 773 K in order to study the kinetics of high-temperature reactions of Fe(2+) and Fe(3+) ions with transient radiolysis species. The radiolytic reactions in a fluid sample within a hydrothermal diamond anvil cell result in oxidation of the Fe(2+) ion at 573 K and reduction of Fe(3+) at temperatures between 673 and 773 K and of the Fe(2+) ion at 773 K. The edge-energy drift evident in the ED-XAS data directly reflects the kinetics of reactions resulting in oxidation and/or reduction of the Fe(2+) and Fe(3+) ions in the aqueous solutions at high temperatures. The oxidation and reduction trends are found to be highly consistent, making reliable determinations of reaction kinetics possible.

Containment of fluid samples in the hydrothermal diamond-anvil cell without the use of metal gaskets: performance and advantages for in situ analysis.

Metal gaskets (Re, Ir, Inconel, or stainless steel) normally used to contain fluid samples in the hydrothermal diamond-anvil cell (HDAC) are sometimes undesirable due to possible contamination and to gasket deformation at high pressures and temperatures resulting in nonisochoric behavior. Furthermore, in x-ray spectroscopic experiments, metal gaskets may attenuate the incident x-ray beam and emitted fluorescence x-rays, and the interaction of scattered radiation with the gasket may produce fluorescence that interferes with the x-ray spectrum of the sample. New arrangements and procedures were tested for the operation of the HDAC without using the metal gaskets. Distilled, de-ionized water was loaded into the sample chamber, a laser-milled recess 300 microm in diameter and approximately 50 microm deep centered in the 1.0 mm face of the lower diamond anvil, and sealed by pressing the top diamond anvil face directly against the lower one without a metal gasket in between. A maximum sample pressure of 202 MPa at 617 degrees C was maintained for a duration of 10 min without evidence of leakage. A small change in fluid density was observed in one experiment where the sample was held at 266 MPa at 708 degrees C for 10 min. The gasketless HDAC was also employed in x-ray absorption spectroscopy experiments, where, in addition to the sample chamber in the lower diamond, two grooves were milled at a 90 degrees angle to each other around the sample chamber to minimize the attenuation of incident and fluorescent x rays. With a minimum distance between the sample chamber and the grooves of 80 microm, a pressure of 76 MPa at 500 degrees C was maintained for 2 h with no change in the original fluid density.

Synchrotron x-ray spectroscopy of EuHNO3 aqueous solutions at high temperatures and pressures and Nb-bearing silicate melt phases coexisting with hydrothermal fluids using a modified hydrothermal diamond anvil cell and rail assembly.

A modified hydrothermal diamond anvil cell (HDAC) rail assembly has been constructed for making synchrotron x-ray absorption spectroscopy, x-ray fluorescence, and x-ray mapping measurements on fluids or solid phases in contact with hydrothermal fluids up to approximately 900 degrees C and 700 MPa. The diamond anvils of the HDAC are modified by laser milling grooves or holes, for the reduction of attenuation of incident and fluorescent x rays and sample cavities. The modified HDAC rail assembly has flexibility in design for measurement of light elements at low concentrations or heavy elements at trace levels in the sample and the capability to probe minute individual phases of a multiphase fluid-based system using focused x-ray microbeam. The supporting rail allows for uniform translation of the HDAC, rotation and tilt stages, and a focusing mirror, which is used to illuminate the sample for visual observation using a microscope, relative to the direction of the incident x-ray beam. A structure study of Eu(III) aqua ion behavior in high-temperature aqueous solutions and a study of Nb partitioning and coordination in a silicate melt in contact with a hydrothermal fluid are described as applications utilizing the modified HDAC rail assembly.

Synthesis of L-kedarosamine in protected form and its efficient incorporation into an advanced intermediate to kedarcidin chromophore.

An efficient route to the complex L-kedarosamine alpha-glycosidic ether 2, a synthetic precursor to kedarcidin chromophore, is described. Central to the route, which is suitable for the preparation of multigram amounts of material, is a short synthetic sequence from D-threonine to protected L-kedarosamine derivatives and methodology for their alpha-selective coupling with appropriate hydroxyl acceptors.

Enaminones 9. Further studies on the anticonvulsant activity and potential type IV phosphodiesterase inhibitory activity of substituted vinylic benzamides.

Structure-activity relationship studies were employed to synthesize a series of 3- and 3,4-substituted benzamides from 3-amino-2-cyclohexenones. An improved method for the synthesis of benzamides from 3-amino-2-cyclohexenones is presented which provided significantly higher yields (71-79%) for the reported compounds. NMR and X-ray structural analyses were undertaken to note the possible intra- and intermolecular interactions of the synthesized analogs. Molecular modeling studies were used to determine the minimized configuration and were compared to their X-ray structures for correlation. These new entities were evaluated as potential anticonvulsants and type IV phosphodiesterase inhibitors (PDE4).

A base-catalyzed solution-phase parallel synthesis of substituted vinylic benzamides from 3-amino-2-cyclohexanones.

An improved method for the synthesis of benzamides from 3-amino-2-cyclohexenones is presented. Using sodium hydride, a base-catalyzed N-benzoylation provided significantly higher yields (71-79%) for the reported compounds. This novel protocol was applied in the solution-phase parallel synthesis of a 12-member library of vinylic benzamide derivatives of 3-amino-2-cyclohexenones in 63-90% yield, using a Radley's Carousel Reaction Station.

Percutaneous endoscopic gastrostomy: an effective strategy for gastrostomy feeding in patients with dementia.

Percutaneous endoscopic gastrostomy (PEG) is an accepted technique for longterm enteral feeding. Its use has increased because of its simplicity and low complication rate. The demands for gastrostomy insertion have risen and now encompass indications where the long-term outcomes are uncertain. Dementia has become one of the commonest indications for gastrostomy feeding. This article reviews the justification for PEG feeding in dementia and suggests a practical approach for this difficult clinical situation. The clinical strategy described in this paper can be applied to other neurodegenerative diseases and provides a framework for improving a PEG service.